The present invention is related to computer network. In particular, the present invention is related to configuring subnets flexibly within a computer network.
Network devices are sometimes stacked together and made into one single device constituting a network. Typically, such network is comprised of switches and a router that are coupled together by a shared bus. By being stacked and enclosed within a casing or chassis, these network devices (also known as stackables) and the shared bus are hidden from view. Only local switch ports of these switches are exposed to a user of the network. As such, hosts of the network is coupled to the network via the exposed local switch ports.
With the availability of a network as a stack of network devices, subnets can be configured within the network. However, possible subnet configurations are restricted by the device boundaries of the network. In particular, all members of a subnet must be connected to local switch ports belonging to a single switch. Or, equivalently, a subnet cannot cross the device boundary of a switch. As a result, subnets cannot be configured flexibly within the network. That is, one or more subnets can be configured on a single switch, yet no subnet can span more than one switch.
The inflexibility in configuring subnets across a switch""s device boundary leads to several drawbacks. One such drawback is the network""s inability to support a mobile network user. Once a host as a member of a subnet commits to a local switch port of a switch, relocating the host to a different switch disqualifies the host as a member of the subnet. Specifically, as a member of the subnet configured in the switch, this member is confined to the device boundary of the switch. Thus, the prior art subnet configuration is not well suited for supporting a mobile network user.
Another problem of implementing such network is inefficiency in forwarding packets between two local switch ports that reside respectively on different switches. Specifically, inter-switch packet forwarding is inherently inefficient for the given stack network architecture because the network architecture necessitates routing for all inter-switch packet forwarding. As such, within the given stack architecture of the network, communication bottleneck is created at the router because the router is frequently overwhelmed by such inter-switch packet forwarding. However, the stack network architecture still has merits. Thus, changing the stack network architecture to eliminate the bottleneck in order to have more efficient packet forwarding is not desirable.
Thus, a need exists for flexibly configuring subnets of the network irrespective of the device boundaries of the switches. Also, a need exists for a more efficient packet forwarding within the network while retaining the benefits of the physical stack network infrastructure without altering the network topology.
Fortunately, as will be explained below, the present invention solves all of the problems stated above with an ingenious network architecture and method for configuring subnets and forwarding packets.
The present invention is drawn to an architecture and method for configuring subnets within a switch network that is typically comprised of switches and a router coupled together via a common shared bus. The present invention enables subnets to be configured flexibly irrespective of device boundaries of the switches. The present invention also offers efficient packet forwarding within the network without altering the network topology, thereby retaining all of the benefits of the network topology without sacrificing performance.
In one embodiment of the present invention, a VLAN-defined (virtual local area network-defined) subnet is configured by mapping a subnet to a VLAN. All subnet members share a single VLAN ID irrespective of device boundaries of the switch network. In particular, in contrast to the span of a conventional subnet, the span of the VLAN-defined subnet is not required to be confined within a single switch""s device boundary. As such, the present invention provides flexibility in configuring subnets. Moreover, an intra-VLAN packet forwarding mechanism is provided for the VLAN-defined subnet such that a packet can be transmitted between any two subnet members. This intra-VLAN packet forwarding mechanism avoids routing even when the VLAN-defined subnet spans more than one switch. Advantageously, packet transmission bottlenecks found typically in the router are eliminated. Finally, in the presence of other of similarly configured VLAN-defined subnets, inter-VLAN packet forwarding can be provided flexibly with or without routing.